Good topic as always, Howie. I've been giving this some thought all day at work, so here are my three cent's worth.
First of all, I've only started to recognize that there is such a thing as the Atomic Age and Copper Age for the last five years or so. I know--I'm stubborn, and don't like revisionist thinking. With that being said, I still believe the Bronze Age ended in 1979. That's they way it was when I was younger, and that's the way it stays as far as I'm concerned.
I would argue that the Copper Age runs from 1980 to 1986. Short, but sweet. My thinking is that the early to mid-eighties was a time of growth for the industry, both creatively and financially. DC was coming out of their implosion of the late seventies, and Marvel had a heavy hand with Jim Shooter that was forging the company into more ambitious directions. On the independent side, books like Teenage Mutant Ninja Turtles were also taking off. The high point was 1986, which many still call the best year in comics (for reasons I probably don't need to explain here--unless you want me to). It was all downhill after that, which leads me to the next Age....
1987-1999. Not sure what to call this. Boom & Bust Age? As far as I'm concerned, the groundwork that led to the comics industry collapsing in the nineties started in 1987, specifically with Jim Shooter being replaced with Tom DeFalco at Marvel. While Jim Shooter pioneered the crossover event at Marvel (with each experiment getting a little bit bigger than the last), it seems Tom DeFalco took it to a whole 'nother level. He started small with some X-Men crossover events that barely affected other books (Mutant Massacre & Fall of the Mutants), but soon made sure that all other Marvel titles would get involved (Inferno, Acts of Vengeance). He also began producing hefty, expensive (for the time) annuals that were always part of a bigger story to buy (collect them all!). It should also be noted that DeFalco began the practice of the gimmick cover with Silver Surfer #50, I believe. These are all things that ultimately contributed to the alienation of fans and the collapse of the market.
2000-2010. I would begin the next age at the year 2000. First, it's a nice round number
. Secondly, this was the year the comics industry started to turn around. I've talked to a lot of shop owners and have asked them when it was that Marvel started to make the turn after their bankruptcy. Most of them tell me it started when Marvel started hiring outside-of-the-box talent for their books, like Brian Bendis and J. Michael Straczynski. Ultimate Spider-Man debuted in 2000, and was so popular that the Ultimate line was once considered to replace the entire mainline Marvel Universe. The year 2000 is also when the first X-Men film hit the big screen, which gave a boost to comics in general, and led to the comic book driven movie industry we have today. Also, love it or hate it, but CGC formed in 2000 and began slabbing books. All would agree that CGC was a significant shot in the arm to the back issue market.
2011-Present. I wouldn't mind saying that our current comic era is still going on since 2000, but I agree that 19+ years is a bit long for one age. It was also mentioned by Swifty that the Variant Age is something we have never seen before in comics. While Marvel and DC did do variants prior to 2011, it really seemed to take off with the New 52, with seemingly almost every single New 52 issue getting a variant cover or three or four (plus reprints). The New 52 also was a creative change at DC, with them dumping all their previous comic history (for the time being). The New 52 was a success, and seems to me to have paved the way for Marvel to do similar reboots and restarts. It's a trend that continues with both companies, and it seems to have started in earnest in 2011.
Anyway. That's what I was thinking.